Handheld geographic information system (GIS) data collection devices are used by utility companies, municipalities, environmental management agencies and others for diverse applications including as-built mapping of power lines, service outage reporting, weed management, water network modeling, etc. An advanced GIS handheld combines a high-accuracy global navigational satellite system (GNSS) receiver, a computer and display, a digital camera, and a cellular data radio in one unit. An operator uses the device to collect position data for utility poles, manhole covers, or myriad other features. Position, images and other data entered by the operator may then be transmitted to a GIS database via the cellular radio data link. As an example of GIS data collection in action, twenty crews of historic preservation surveyors used GIS handhelds to record locations and condition of over 40,000 historic homes in six parishes of post-Katrina New Orleans. The data for each home included precise geospatial coordinates, structural descriptions using a local dictionary of housing terms from the Louisiana State Historic Preservation Office, flood damage data, and photographs.
In some GIS survey situations it is hard to reach an object whose position is needed. A high-voltage transformer may be located behind a protective fence, for example, or the top of a pile of coal may be growing or unstable. In these and many other situations an operator may find the position of an inaccessible object by using a laser rangefinder to estimate the distance from a GIS handheld to the object. Given the location of the GIS handheld and the range and bearing to the inaccessible object, the object's location can be estimated.
A GIS handheld with a laser rangefinder and a camera is useful for obtaining digital images that are automatically tagged with position data for objects that the camera is aimed at. The camera may display cross-hairs in a video viewfinder mode to help an operator aim directly at an object such as a water pipe in a trench. For accurate results the camera and rangefinder must be aligned so that the cross-hairs in the camera image correspond to the point measured by the laser rangefinder. In some implementations the laser rangefinder, although itself operating with an infrared laser, includes a pre-aligned spotting laser operating at visible wavelengths. This is helpful both for human observers who can't see infrared light and repurposed consumer digital cameras that have infrared blocking filters. What are needed, therefore, are systems and methods to align a laser rangefinder (or its spotting laser) and a digital camera.
A GIS handheld provides just one example of the utility of finding a spot in a digital video image. A similar example is provided by a laser gun sighting system in which a digital camera acts as a target scope and a laser illuminates a target. In that case it is helpful to align the camera and laser to each other and to the barrel of the gun. Even more generally, many other situations require finding a spot in a video image. The spot may be illuminated by a laser or may itself be a light source such as a light-emitting diode (LED). Thus what are needed are systems and methods for video alignment with optical sources.